ENGINEERING SERVICES

THERMODYNAMIC CYCLE ANALYSIS

New technical challenges for supporting increased energy conservation and reduced Green House Gas (GHG: carbon dioxide gas) have emerged in recent years.  In response, HTRD has developed an analytical tool to predict the impact of various energy systems on these two important issues.

This simple analytical tool shows us to predict  overall power generation output that utilize waste heat discharged from sources such as industrial facilities, geothermal heat sources, solar power generating systems, etc.   The fundamental principle for this analytical tool lies in the thermodynamics of Rankine cycle.

The working fluids for the Rankine cycle are composed of water, organic fluids of different kinds, or mixture of binary fluids.  The temperature of the heat sources, will determine the appropriate fluids to be used.  For example, where high pressure steam of water is available as a waste heat source, water Rankine cycle is used for driving steam turbines to generate power.  The efficiency of these systems is high; therefore, in most large power plants including the nuclear, water Rankine cycle is used. 

There are times when steam Rankine systems are not the optimal solution due to their high specific volume at low pressure at the condenser, In these cases, Organic Rankine Cycle (ORC) systems are used where heat sources are at moderately low temperatures and compactness is required.  Sometimes, a combined cycle of a water-basedr Rankine Cycle system bottomed by an ORC system is used to take advantages of the two respective cycles. 

A binary fluid cycle is a new concept attempting to extract waste heat from low temperature heat sources such as ocean water temperature differential between the ocean surface to a deeper zone that is at a lower temperature . These types of binary cycles where a mixture of ammonia and water is used in the system are generally called Kalina Cycles.  The efficiency of Kalina cycle, however, is very low (6-8%) but unfortunately, the efficiency of ORC cycle is even lower in such cases.. A recent technology of modified Kalina Cycle known as Neogen Cycle intends to increase the cycle efficiency higher than the ORC and also at higher temperature heat source temperatures

However, in most of the practical applications, we are more interested in harvesting thermal energy via ORC systems because the ORC is a matured, proven technology and there are enormous amount of waste heat sources at moderate temperatures (100 – 350 C) are already available and the efficiency is high ion the temperature range.